Here are some things to know about what New Zealand Prime Minister Jacinda Ardern called “one of New Zealand’s darkest days”:

The first shooting occurred at the Masjid Al Noor mosque near Hagley Park in central Christchurch around 1:45 p.m. local time. The shooting took place during Friday prayers, police said. The second shooting took place in another Christchurch mosque on Linwood Avenue, police said.

The shootings at the Christchurch mosques are now the deadliest in New Zealand’s history, TVNZ reported. The 40 people confirmed killed Friday topped the 1990 Aramoana massacre that claimed 13 lives.

Thousands of students were in lockdown in schools across Christchurch, but police have since lifted it, allowing parents to be reunited with their children.

A man who claimed responsibility for the shootings left an anti-immigrant manifesto, according to The Associated Press. In the manifesto, the man explained who he was and gave his reasons for his actions. The man said he considered his actions a terrorist attack, according to the AP.

Videos that appeared to show the the shootings have been taken down from social media, Mia Garlick, a spokeswoman for Facebook New Zealand, told CNN. "New Zealand Police alerted us to a video on Facebook shortly after the livestream commenced and we quickly removed both the shooter’s Facebook and Instagram accounts and the video," Garlick told CNN. Twitter has also removed the video, CNN reported.